[PATCH] autom4te: Handle m4 traces without file:line

The symptoms are something like:

  Use of uninitialized value $msg in concatenation (.) or string
   at /usr/local/Cellar/autoconf/2.69/bin/autom4te line 1032.
  Use of uninitialized value $stacktrace in pattern match (m//)
   at /usr/local/Cellar/autoconf/2.69/bin/autom4te line 1032.
  unknown channel m4trace: -1- AS_VAR_APPEND(ac_configure_args, " '$ac_arg'")
   at /usr/local/Cellar/autoconf/2.69/share/autoconf/Autom4te/Channels.pm line 638.

The root cause is m4 traces without a file/line number shown.

So instead of something like:

   m4trace:configure.ac:48: -1- ...

you have something like:

  m4trace: -1- ...

The issue was first reported by Christophe de Dinechin as bug #25740:
  https://lists.gnu.org/archive/html/bug-automake/2017-02/msg00002.html

He then provided two variants of the fixes in the thread:
  https://lists.gnu.org/archive/html/bug-automake/2017-03/msg00003.html

The first fix skips errors that can't be handled by autom4te.
The second one sets file and line number to placeholders.
This is a resend of the second fix.

Signed-off-by: Christophe de Dinechin <[email protected]>
Signed-off-by: Roman Bolshakov <[email protected]>
---
 bin/autom4te.in | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/bin/autom4te.in b/bin/autom4te.in
index abe6327d..de4d96b4 100644
--- a/bin/autom4te.in
+++ b/bin/autom4te.in
@@ -829,6 +829,9 @@ EOF
       # Traces without arguments, always on a single line.
       s{^m4trace:(.+):(\d+): -(\d+)- ([^)]*)\n$}
        {AT_$4([$1], [$2], [$3], [$4])\n};
+      # Traces without file and line number.
+      s{^m4trace: -(\d+)- ([^(]+)\((.*)$}
+       {AT_$2([nowhere], [0], [$1], [$2], $3};
       print $trace_m4 "$_";
     }
   $trace_m4->close;
-- 
2.19.1